Glue and process of manufacture therefor



I06. COMPOSITIONS,

COATING OR PLASTIC.

V m Patented Mar. 18, 1941 oFFlcg m fla UNITED smig me Wu, W'

GLUE AND PROCESS OF MANUFACTURE THEREFOR No Drawing.

Application October 27, 1937,

Serial No. 171,322

11 Claims.

This invention relates to a new and improved glue and the proces of manufacture thereof, and has particular reference to a reagent for extending proteinaceous glues.

More particularly, the invention relates to the use of a class of chemicals commonly called tannins, to be found in oak bark, hemlock bark, pi'ne'bark, chestnut wood, quebracho, and a large variety of other vegetable origins, or the use of veetable P0 as a reagent for use in extending glues made from colla en.

It is an objTa'cto'f the present invention to provide a new process for preparing proteinaceous glues; to provide a new product derived from animal and vegetable origin; to provide a new process for treating proteinaceous glue whereby it is converted into an adhesive having new and useful properties; to provide a process for extending proteinaceous glues and at the same time improve their adhesive qualities; to provide a process for increasing the amount of wet glue to be derived from a given amount of dry glue base; and to provide a reagent for extending proteinaceous glues.

Commercial animal glue is derived from collagen by hydrolysis to produce a substance soluble in hot water. As is well known, collagen is found in the sinews, ossein, fleshings and hide scrap of animals. Such raw material usually is referred to as glue stock. These collagen-comtaining materials, after being appropriately treated to remove some of the grease, hair, dirt and other foreign substances, are subjected to the action of heat and water. Collagen is not soluble in hot water, but when it has been subjected to a suficient degree of hydrolysis it is converted into gelatin which is soluble in hot water. In the conventional manufacture of animal glue the collagen contained in the glue stock is hydrolyzed until it is converted into gelatin and passes into solution in hot water. Thereupon the solution is extracted from the insoluble portion of the stock and clarified, concentrated, chilled and dried, commonly in the form of flakes. The dry glue is converted into the final adhesive by dissolving it in hot water in which it disperses readily because of its solubility.

In one aspect of the present invention, reference is made to a glue base derived by hydrolyzing collagen-containing matter, in the manufacture of which it is necessary to hydrolyze the collagen, but not to a degree which produces gelatin; and the glue base which is the product thereof is substantially insoluble in hot water. The degree of hydrolysis of collagen suflicient to produce this glue base, but which is insufficient to produce gelatin, is herein termedm tion of the collagen into gelatin.

A further characteristic of the hereinabove described glue base is that the product of collagen hydrolysis is not extracted from the glue stock, the disintegration and dispersion of the glue stock being accomplished by mechanical means. This is in contrast to the careful separation made in the manufacture of gelatin or animal glue, in which the hydrolytic derivative of collagen is dissolved in hot water and then extracted from the glue stock and subsequently further purified by filtration, etc. In the process of producing the glue base hereinabove described no chemical separation is made of the hydrolytic derivatives of collagen from the non-collagen protein substances with which the collagen is associated in the glue stock. The glue base may be described, therefore, as the hydrolysis product of protein matter containing unextracted collagen hydrolyzed to a degree intermediate between collagen and gelatin and insoluble in hot water, or as the hydrolysis product of protein matter containing unextracted collagen hydrolyzed to the extent of converting only a portion of the collagen into gelatin.

In addition to the above outlined process for preparing a glue base which is insoluble in hot water, a glue base may be produced by hydrolyzing the collagen sufiiciently to form glue or gelatin which is soluble in hot water. This so.- lution is drawn on at suitable intervals and is clarified, concentrated, chilled and dried. The dried product is commonly in the form of flakes,

although it has been found that the glue goes into solution more readily when in a more finely divided form. It is deemed proper, for the purposes of the present disclosure, to describe this particular lue base as being of a gelatigenous character, soluble in hot water. mrdamdure of the present invention, a small amount of a vegetable tannin, or leather tanned with ve etabm is substituted for a like amount of the dry glue base which serves to extend the wet glue byFe'? ii fitting a higher ratio of water to dry ingredients without loss of adhesive qualities. Also, it has been discovered that the use of either a vegetable tannin or vegetable tanned leather and a higher water ratio improves the strength and water resistance of the bond.

Since the glues referred to are derived from collagen, which is principally found in the hides, bones, sinews and fieshings of animals, a convenient method of utilizing the reagent properties of vegetable tannins is through the use of vegetable tanned leather, which is a combination of collagenous material with tannins. It should be understood, however, that while vegetable tanned leather, as called for in the formulae hereinafter set forth, gives especially good results and so may be used as a matter of convenience, a

vegetable tanning material, such as uebracho may be used in place thereof to produce the desired results. In this connection it should also be stated that chromglannedleathg is not useful in applicants process.

The leather should first be ground to a powder or flour, and to expedite this the leather scrap may be subjected to an atmosphere of steam at 212 F. for a period of from fifteen to thirty minutes, after which it is dried and ground.

The following comparative formulae for the preparation of high grade animal glue (215 grams, Bloom gelometer test) illustrate the reagent properties of the leather for extending glue consisting of a glue base of a gelatigenous character, soluble in hot water. In the first formula no leather or vegetable tannin is used; whereas, in the second formula 5 parts of leather flour is substituted for 5 parts of glue base, the ratio of dry glue base to water being thereby increased from 1:7 to 1:9. Especially good results are obtained if the leather powder is dissolved in tc; by the action of caustic soda before it is added to the glue g Animal Caustic glue Leather Sada Lime Silicate Water No. l.-. 100 4 3 $88 No. 2... 5 6 3 8O 7: 1am,- m-flnkl mnl .u a luwcl; g1 ade of water auluuse an...u glue has is used, less water may be used. For example, if a glue base which grades 108 grams by the Bloom 'gelometer test is substituted in the above formula, and five parts of leather are substituted for five parts of glue base, the amount of water would be reduced to 450 parts. The formula would thereupon read as follows:

4 Animal glue Caustic Lime Silicate Water Without the substitution or addition of a vegetable tannin or leather tan ned with vege tabletanninfa formula consisting chiefly'of low grade animal glue will not produce an adhesive satisfactory for gluing wood.

Applicant has discovered that the use of leather with colla enou lues is particularly advantageous in e manufacture of plywood by the hot pressing process. Aside from extending the glue by permitting a higher water ratio, it definitely improves the strength and water resistance of the bond formed. It is a peculiarity of collagenous glues that their viscosities are greatly affected by temperature. A rise in temperature decreases their viscosity sharply. When such glues are used in the hot pressing process there is a tendency for them to become too fluid and therefore to penetrate too much into the wood, producing an inferior glue bond. The use of vegetable tanned leather or tannin, as herein set forth, greatly reduces this harmful effect of heat. This is also of great importance in the cold press process when, as is often the case, veneers are glued while they are still hot from the drying operations.

In the following comparative formulae the lue base is composed of a hygrglytic product 0:

- u tween collaen and sake of convenience, it may be Ossein Caustic Leather Soda Lime Silicate Water No.4.-. No. 5...

In each of the illustrative formulae hereinabove set forth, the ratio of leather to glue base is 5:95. The amounts thus indicated are purely arbitrary, however, since as great an extension of the glue by use of a higher water to dry ingredients ratio is to be had with the use of as little as two parts of leather to ninety-eight parts of glue base. On the other hand, a considerable increase in the proportion of leather to glue base diminishes certain outstanding advantages of the glue, notably, its resistance to the detrimental effect of long assembly time and its lack of staining. When leather is substituted for a portion of the glue base, it is desirable to increase the amount of caustic soda used in the formula. If the amount of leather in the formula isyaried, the amount of caustic soda should be varied proportionately. In the manufacture of glues intended for use in cold press operations, the variation in amounts of leather and caustic soda is as follows:

Parts Leather Parts Caustic soda 6 Leather Caustic soda 8 Leather 15 Caustic soda 10 Leather 20 Caustic soda 12 In general, glues for hot press operations may contain a lower proportion of caustic soda.

Of first importance in the process of utilizing the properties of leather flour as a reagent to extend the glue is the use of heat. Whereas the use of leather in the formula, with water at ordinary room temperature (70 F.), extends the glue, it is further extended if heat is applied during the initial steps of preparing the wet adhesive. For example, in formula No. 4, the glue base composed of the hydrolytic derivative of ossein alone may be prepared at a ratio of dry glue base to water of 1:8. By the use of leather, the ratio can be extended, as indicated in formula No. 5, to 1:10; and by the use of leather and an increase in the temperature of the mixture during initial steps of preparation, the ratio of dry glue base to water can be extended further to 1:11, This increase in water ratio increases the amount of wet glue derived from a given amount of dry glue base; and, without increasing the amount of wet glue spread over a given area, satisfactory results are obtained with the extended glues. As long as the amount of wet glue spread is kept constant, the amount of dry glue spread decreases with an increase in the dilution of the glue.

In accordance with the preferred procedure, heat is initially applied to the mixture by the use of water at 100 F. The solution may, however, be subjected to extraordinary, or. violent,

I06. COMPOSITIONS,

COATING OR PLASTIC.

Exami I mechanical agitation, as by means of a gear pump, the internal friction or fluid shear created thereby being sufiicient to increase the temperature of the mixture to the desired point. In 5 favor of the use of a gear pump is the fact that the glue base need be but very coarsely ground, thus eliminating the expense of fine grinding, the action of the pump being to tear the coarse particles apart and disperse them in the solution. l Whichever method is used to initially increase the temperature of the mixture, it should be finally cooled to ordinary room temperature (70-80 F.) to prevent too rapid hydrolysis of the glue base. When extraordinary mechanical l agitation is used, the mixture may be cooled by passing through cooling coils. If water at 100 F. has been used, the mixture may be cooled at the proper time by the addition of cold water, or by some external cooling means. so A formula embodying applicant's process for use with either vegetable tanned leather or a vegetable tanning material is as follows:

Parts Waterat 100 F 500 25 Processed oss 95 Pr d leather, or guebracho 5 In a formula employing high grade animal glue instead of ossein, 400 parts of water at 100 F. may be used initially; 50 parts of water are added with the caustic soda and lime in solu- 40 tion; and 400 parts of water (cold) are added to cool the mixture to room temperature before the silicate of soda is added. In other words, the form ae d1 er only in the amount of water used. Having now described my invention and in 45 What manner the same may be used, what I claim as new and desire to protect by Letters Patent is: 1. The process of making a collagenous glue having an adhesive value suitable for gluing wood, which comprises subjecting protein matter 50 containing collagen to the hydrolytic action of heat and water sufiicient to convert a portion of the collagen into gelatin and limited so that a portion of the collagen remains insoluble in water at 95 F., and increasing the aqueous con- 55 tent thereof by combining therewith in an aqueous alkaline medium a vegetable tannin, the ratio of aqueous content to protein content being greater than four to one.

2. The process of making a collagenous glue 60 of high aqueous content and having an adhesive value suitable for gluing wood, comprising combining a hydrolysis product of collagen and a vegetable tannin in the presence of an aqueous medium containing sufiicient alkali to maintain 65 an alkaline reaction in said medium, the ratio of aqueous content to protein content being greater than four to one.

3. The process of making a collagenous glue of increased aqueous content and having an ad- 70 hesive value suitable for gluing wood, comprising combining a hydrolysis product of collagen and a vegetable tannin in an aqueous alkaline medium, and adding water in sufiicient volume to create a ratio of aqueous content to protein content greater than four to one.

4. The process of making a collagenous glue of high aqueous content and having an adhesive value suitable for gluing wood, comprising combining in an aqueous alkaline medium a collagenous glue and vegetable tannin, the ratio of the aqueous content to the protein content in said mixture being greater than four to one.

5. A collagenous glue suitable for gluing wood and having a water content in excess of four times its protein content and spreadable at a temperature below 92 F., comprising as its principal adhesive constituent a hydrolysis prodnot of collagen, a vegetable tannin, and an alkali metal silicate, the alkaline content being in sufficient quantity to react with the tannin.

6. The process of making a collagenous glue suitable for gluing wood, comprising combining a hydrolysis product of collagen and a vegetable tanned leather in the presence of an aqueous alkaline solution at substantially 100 F. and containing sufiicient alkali to maintain an alkaline reaction in said solution, and then cooling said solution to ordinary room temperature, said glue solution containing an aqueous content of four times its protein content.

'7. The process of making a collagenous glue of high aqueous content and having an adhesive value suitable for gluing wood, comprising combining vegetable tannin with an aqueous dispersion of a hydrolysis product of collagen, said dispersion containing an aqueous content of four times its protein content, and maintaining therein an alkaline reaction.

8. The process of making a collagenous glue of high aqueous content and having an adhesive value suitable for gluing wood, comprising combining with the collagenous glue a vegetable tannin and dispersing said composition in an aqueous alkaline medium, the ratio of aqueous content of said glue to protein content being greater than four to one.

9. A collagenous adhesive composition suitable for gluing wood and having a water content in excess of four times its protein content, comprising as its principal adhesive constituent a hydrolysis product of collagen, a vegetable tannin and an alkali metal silicate, the alkaline content being in sufiicient quantity to react with the tannin.

10. A collagenous adhesive composition suitable for gluing wood and having a. water content in excess of four times its protein content, comprising as its principal adhesive constituent collagenous matter insoluble in water at 100 F. resulting from subjecting collagen to the hydrolytic action of heat and water su ificient to convert a portion only of said collagen into gelatin, a vegetable tannin, and an alkali metal silicate, the alkaline content being in sufiicient quantity to react with the tannin.

11. The process of making glue comprising subjecting protein matter containing collagen to the action of heat and water suflicient to convert a portion of said collagen into gelatin and limited so that a portion of the collagen contained therein remains insoluble in water at 100 F., and subjecting the resulting mixture of gelatin and hot water insoluble protein matter to mechanical disintegration, and combining therewith a vegetable tannin in an aqueous alkaline medium having an aqueous content in excess of four times its protein content.

CHARLES N. CONE. 

